With the development of genetic engineering technology, it has become possible to use physiologically active proteins such as antibodies, enzymes, hormones and cytokines as pharmaceutical products. To supply them in stable amounts with high quality, it is necessary to establish preparation conditions and storage conditions under which the structure and activity can be maintained.
Generally, a problem encountered during storage of proteins is a deterioration phenomenon such as the formation of insoluble aggregates and must be prevented.
For example, antibodies such as immunoglobulins, monoclonal antibodies and humanized antibodies are unstable proteins liable to physical or chemical changes such as association or aggregation under stresses of filtration, concentration and heat during purification and formulation processes as well as stresses of heat, light and transportation during storage of stock solutions or formulations.
When antibodies are to be obtained by genetic engineering techniques, antibody-producing cells are cultured in bulk and purified to give an antibody-containing solution, which is then stored frozen and thawed before formulation. However, the antibody content remaining in such a solution decreased as antibody dimers or insoluble particles or foreign insoluble matters were formed during repeated freeze/thaw cycles or antibodies were degraded to form degradation products during long-term storage.
In order to inhibit the formation of such foreign insoluble matters and to obtain stable protein-containing formulations, the use of surfactants is indispensable, and especially, such surfactants as polysorbates 20 and 80 have been widely used. In the case of readily oxidizable protein formulations, however, antioxidants such as L-methionine had to be included in addition to polysorbate 80 (JPA No. 2000-247903, J. Pharm. Sci. 90:3 (2001)) because polysorbate 80 tends to oxidize proteins (PDA J. Pharm. Sci. Technol. 50:3(1996); Formulation, Characterization, and Stability of Protein Drugs. Plenum Press, New Yolk, (1996)), thereby lowering the biological activity of antibody formulations. The addition of antioxidants required complex operations such as strict determination of the specifications and amounts of the antioxidants.
Thus, it would be desirable to provide a surfactant capable of inhibiting the oxidation of proteins without adding antioxidants and capable of inhibiting the formation of foreign insoluble matters in protein formulations. Lyophilized formulations can inhibit the oxidation of proteins (for example, JPA No. 2000-247903), but there are great demands for convenient solution formulations eliminating the reconstitution step and it would also be desirable to provide protein-containing formulations that are stable even as solution formulations.
An object of the present invention is to find a surfactant capable of inhibiting the oxidation of proteins without adding antioxidants to maintain the biological activity of the proteins and also capable of inhibiting the formation of foreign insoluble matters in protein formulations and to provide a stabilized protein-containing formulation containing said surfactant.